Low-angle normal fault complexes provide numerous possibilities for unique younger-over-older geometries that may place organic-rich source facies in fault contact with potential reservoir sections. Various geometric scenarios can be developed depending on the chronologic development of low-angle and spatially associated high-angle normal faults. In many ranges, several low-angle faults are exposed and either merge with or cut one another. These low-angle faults are also cut by high-angle faults or in some cases the low-angle faults displace older high-angle normal faults. Thus, complex structural styles that place source and reservoir together and utilize low-angle and/or high-angle normal faults as an element of closure are possible. Possible trap styles developed as updip truncations in low-angle normal fault settings are illustrated on Figure 3.

The structural setting of the Grant Canyon oil field along the western flank of the Grant Range appears to be complicated by low-angle normal faults. Closely spaced wells penetrate stratigraphic units at approximately the same structural level that are normally separated by thousands of feet of section. This suggests attenuation and structural juxtaposition along extensional low-angle faults. Overall, the closure in the Grant Canyon field is controlled by major high-angle normal faults with the overlying Tertiary unconformity as a seal.

Major stratigraphic attenuation along low-angle normal faults can and often does eliminate both the potential Paleozoic reservoir and source sections. These traps are very difficult to predict within the basin. Plays based on such a trap will be very high risk.